Background: 3 spray arms. Top 2 did not rotate. Cleaned both removing deposits, cleaned coarse and fine filters. Ran CLR through entire wash cycle.
Two lower spray arms turn, top arm does not. No blockage in conduit supply line, as I pulled a knotted string through it. The service port for the middle spray arm (on the conduit) has two grooves which look to be for O -rings (?) but there are no O rings on it. Bought regular Oring at hardware store, but no difference in top spray arm. Water level in unit is at spec level.
What next for trouble shooting and repair? Its crazy!